The present claimed invention relates to a responsive glass membrane for ion selective electrode having a self cleaning function and an ion selective electrode comprising the responsive glass membrane.
Conventionally, it has been known that crystalline titanium dioxide (TiO2, titania) of rutile type or anatase type has photocatalytic activity. Powerful oxidation-reduction properties and superhydrophilic properties are represented as the photocatalytic activity; disinfection treatment is applied to a wall or a floor of a surgery room in a hospital by coating the wall or the floor with titanium dioxide and irradiating it with the ultraviolet radiation by making use of the oxidizing properties of superoxide ion formed in the degradation of H2O, antifog treatment is applied to a side mirror of an automobile or a mirror on a road by coating the mirror with titanium dioxide so that self cleaning can be conducted when it rains by making use of the superhydrophilic properties, or the superhydrophilic properties is also applied to taint prevention of an exterior wall of a building or a sheet for a tent.
The responsive glass membrane of the ion selective electrode such as a pH electrode is usually made of silicate glass, and it requires sufficient washing by the use of distilled water or the like every time measurement is conducted in order to keep an accuracy of the measurement. In addition, it requires calibration of pH or the like after washing.
With the view to these properties, if the photocatalytic activity of titanium dioxide can be utilized for the responsive glass membrane, it is considered that the responsive glass membrane can be easily washed and that an ion selective electrode requiring no calibration can be obtained as well.
However, if the photocatalytic activity is given to the responsive glass membrane of the ion selective electrode by crystalline titanium dioxide, an electrical potential fluctuation might occur due to generation of hydroxyl by the superhydrophilic properties, oxidization properties might be performed on a sample solution as being an object to be measured so as to degrade or change its component. As a result of this, it has not been tried that titanium dioxide is applied to the responsive glass membrane with intent to give the photocatalytic activity.
In addition, if a concentration of lithium oxide in the glass is high, it is alleged that an electric resistance decreases in general. As a result, if the glass containing a lot of lithium oxide is used for the responsive glass membrane of the ion selective electrode, there is a possibility that varieties of effects due to low electric resistance can be obtained; for example, response is improved, no necessity to use expensive materials such as Teflon (registered trademark) for connectors because high insulation properties is not required for electric wiring sections and some dust may be permitted in an assembling environment, in addition to a self cleaning effect because of titanium dioxide.
Then the present claimed invention intends to provide a responsive glass membrane for ion selective electrode glass and an ion selective electrode comprising the responsive glass membrane that produces a self-cleaning function when the ultraviolet rays are irradiated although no change is brought in a composition of a sample solution as being an object to be measured under an ordinary measurement environment and that is low in electric resistance value and superior in sensitivity.